[r2005-08-29 11:48:44 by afrisch] Add an example

Original author: afrisch
Date: 2005-08-29 11:48:44+00:00

web/ocaml.xml

@@ -1226,6 +1226,32 @@ Some features of XML Schema are not parsed, such as
 
 </section>
 
+<section title="String regular expressions">
+
+<p>
+OCamlDuce supports regular expression types and patterns, not only
+for sequences of XML elements, but also for strings. The following
+example shows how to use regular expressions to split a string
+of the form <code>name1=val1,...,namen=valn</code> with
+<code>n>0</code> into
+a list of pairs <code>[ (name1,val1); ...; (namen,valn) ]</code>.
+The <code>*?</code> operator in regular expressions means ``ungreedy
+match'' (match the shortest possible subsequence). The last
+pattern describes precisely strings which are not matched by
+the other cases. It would be possible to replace it with
+the wildcard <code>_</code>.
+</p>
+
+<sample><![CDATA[{{ON}}
+let rec split (s : {{ String }}) =
+  match s with
+    | {{ [ n::_*? '=' v::_*? ',' rest::_* ] }} -> (n,v)::(split rest)
+    | {{ [ n::_*? '=' v::_*? ] }} -> [ (n,v) ]
+    | {{ Any - [ _* '=' _* ] }} -> failwith "split"
+]]></sample>
+
+</section>
+
 </box>
 
 </page>
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